Method for supporting indication of a failure event to a source access system

ABSTRACT

A method for supporting indication of a failure event to a source access system is provided. The method includes notifying, by the source access system, information of a source cell to a target access system, routing, by the target access system, a message to the base station or the base station controller of the source access through a core network by use of the information of the source cell received from the source access system when the target access system needs to transmit a message to the source access system. By use of the method provided by the present disclosure, a problem of mobility robustness optimization (MRO) among different radio access technology (RAT) may be notified to the source access system, so as to avoid impact for a terminal, reduce operator configuration.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/657,857, filed on Jul. 24, 2017, which is a continuationapplication of prior application Ser. No. 14/430,311, filed on Mar. 23,2015, which issued as U.S. Pat. No. 9,730,115 on Aug. 8, 2017, which isa U.S. National Stage application under 35 U.S.C. § 371 of anInternational application filed on Sep. 17, 2013 and assignedapplication number PCT/KR2013/008390, which is based on and claimedpriority of a Chinese patent application filed on Sep. 21, 2012 in theState Intellectual Property Office and assigned Serial number201210359119.9, the entire disclosure of each of which is herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to mobile communication system field.More particularly, the present disclosure relates to a method forsupporting indication of a failure event to a source access system.

BACKGROUND

With the development of communication technology, a mobile communicationsystem has developed to a system of system architecture evolution (SAE).

FIG. 1 is a schematic diagram illustrating a structure of an SAE systemaccording to the related art.

Referring to FIG. 1, the SAE system includes an evolved universalterrestrial radio access network (E-UTRAN) 101 and at least includes amobility management entity (MME) 105 and a core network of a user planeentity (i.e., a serving-gateway (S-GW)) 106. The E-UTRAN 101 is used toconnect a user equipment (UE) to the core network. Moreover, the E-UTRAN101 also includes more than one macro base stations (i.e., an evolvednode B (eNB)) 102 and home base stations (i.e., a home eNB (HeNB)) 103,optionally includes a home base station gateway (HeNB GW) 104, the MME105 and S-GW 106, which may be integrated into one module forimplementation, or may be separated to be implemented individually.Herein, inter-connection between eNBs 102 is through an X2 interface.The eNB 102 is connected respectively to MME 105 and S-GW 106 through anS1 interface. Alternatively, the eNB 102 is connected to the optionalHeNB GW 104 through the S1 interface, the HeNB GW 104 is connectedrespectively to the MME 105 and the S-GW 106 through the S1 interface.

In an early state of establishing the SAE system or during a process ofoperating the SAE system, much manpower and material resources are takento configure and optimize parameters of the SAE system, especially toconfigure wireless parameters, so as to ensure good coverage andcapacity of the SAE system, mobility robustness, load balancing whenmoving and speed of accessing user device, and the like. In order tosave the manpower and material resources for configuration during SAEsystem operation, a method for self-optimizing the SAE system iscurrently proposed. During a self-optimization operation, eNBconfiguration or HeNB configuration is optimized actually according to acurrent state of the SAE system. The eNB and HeNB are referred as to eNBhereinafter to instruct the method for self-optimizing the SAE system.

FIG. 2 is schematic diagram illustrating a basic principle ofself-optimizing an SAE system according to the related art.

Referring to FIG. 2, after the eNB powers up or accesses SAE, theself-optimization configuration may be performed. The operation includeseNB basic configuration and initial wireless parameter configuration.Herein the eNB basic configuration includes configuration of an internetprotocol (IP) protocol address of the eNB, operation administration andmaintenance (OA & M), authentication between the eNB and the corenetwork. When the eNB is the HeNB, it is needed to detect the HeNB GW towhich the HeNB belongs. Software and operation parameters of the eNB aredownloaded to perform self-configuration. Initial wireless parameterconfiguration is implemented according to experience or simulation.Performance of each eNB in the SAE system may be impacted by environmentof region where the eNB locates. Thus, the eNB needs to perform initialconfiguration of a list of neighbor cells and initial configuration ofthe load balancing specifically according to initial wireless parameterconfiguration of the environment of the region where the eNB locates.After the self-configuration operation is completed, many parametersconfigured for the eNB are not optimized.

In order to make the performance of the SAE system better, configurationof the eNB is needed to be optimized or adjusted, which is also calledself-optimization of the mobile communication system. When theconfiguration of the eNB is to be optimized or adjust, the eNB may becontrolled by the OA &M in a background to execute it. A standardinterface may exist between the OA & M and the eNB. The OA & M transmitsthe parameters to be optimized to the eNB (which may be the eNB or theHeNB) through the interface.

Thereafter, the eNB optimizes the parameters configured to the eNBitself according to the parameters to be optimized. The operation may beexecuted by the eNB itself. For example, the eNB performs detection toobtain the performance to be optimized, performs optimization andadjustment to corresponding parameters of the eNB itself. Optimizationor adjustment of eNB configuration may include self-optimization of thelist of neighbor cells, self-optimization of the coverage and thecapacity, self-optimization of mobility robustness, self-optimization ofthe load balancing, self-optimization of parameters of a random accesschannel (RACH), and the like.

Hereinafter, a basic principle of the self-optimization of the mobilerobustness in Release 10 is described. When a radio link failure (RLF)or a handover failure occurs for the UE and the UE returns to aconnection mode, the UE indicates that the UE has an available RLFreport to the network. The network transmits a message to the UE torequest the RLF report. The RLF report transmitted by the UE includesinformation of an e-UTRAN cell global identifier (ECGI) of a cellserving the UE lastly, an ECGI of a cell to which re-establishment istried, an ECGI of a cell where a handover operation is, triggeredlastly, time from handover triggered lastly to a connection failure,whether a reason of the connection failure is a RLF or handover failure,radio measurement. A base station obtaining the RLF report of the UEforwards the RLF report obtained from the UE to a base station of thecell serving the UE lastly. The base station of the cell serving the UElastly determines whether the reason is too early handover, too latehandover, handover to an error cell or a coverage hole. If the reason isthe too early handover or the handover to an error cell, the basestation transmits information of the too early handover or the handoverto an error cell to the base station which triggers the too earlyhandover or the base station where the UE is handed over to an errorcell.

Therefore, a need exists for a method for supporting indication of afailure event to a source access system to avoid impact for a UE, reduceoperator configuration, transmit a handover report to the source accesssystem correctly, and improve performance of a mobile communicationsystem.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present disclosure.

SUMMARY

For Mobility Robustness Optimization (MRO) between different radioaccess technology (RAT), e.g., too early handover from the 3^(rd)Generation (3G) or 2^(nd) Generation (2G) to long term evolution (LTE),a radio link failure (RLF) occurs for the user equipment (UE) in evolvedNode B1 (eNB1) when the radio network controller (RNC) just hands overthe UE to eNB1 successfully. When accessing LTE next time, the UEtransmits an RLF report to an accessed eNB (e.g., eNB2). The eNB2transmits a RLF indication message to eNB1. The eNB1 determines thereason of the failure. If the reason is too early inter-RAT handover,the eNB1 transmits a handover report to the RNC. The eNB1 needs totransmit a handover report to a source RNC through the core network.Through the RLF indication message, the eNB1 may know a cell identifierof a source cell. But the eNB1 does not know other location informationof the source cell, so that the eNB1 cannot route the handover report tothe source RNC.

Aspects of the present disclosure are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentdisclosure is to provide a method for supporting indication of a failureevent to a source access system to avoid impact for a UE, reduceoperator configuration, transmit a handover report to the source accesssystem correctly, and improve performance of a mobile communicationsystem.

In accordance with an aspect of the present disclosure, a method forsupporting indication of a failure event to a source access system isprovided. The method includes notifying, by the source access system,information of a source cell to a target access system, andtransmitting, by the target access system, a message to the sourceaccess system when the target access system needs to transmit themessage to the base station to which the source cell belongs. Thereceived information of the source cell is used to routing the messageto the source access system.

It should be noted that the source access system notifies theinformation of the source cell to the target access system throughhandover preparation.

It should be noted that the information of the source cell comprises oneor more of the following information: a cell identifier of the sourcecell, a location area identity (LAI) to which the source cell belongs, arouting area code (RAC) to which the source cell belongs, an identifierof the RNC to which the source cell belongs, an extended identifier ofthe RNC to which the source cell belongs, and a tracking area identity(TAI) to which the source cell belongs.

It should be noted that the message includes the cell identifier of thesource cell, and/or the LAI and the RAC to which the source cellbelongs, and/or the identifier of the RNC to which the source cellbelongs, and/or the extended identifier of the RNC to which the sourcecell belongs, and/or the TAI to which the source cell belongs when thetarget access system transmits the message to the base station to whichthe source cell belongs.

It should be noted that a node of a target core network finds a node ofa source core network according to the LAI and RAC or TAI to which thesource cell belongs.

It should be noted that when the source access system is 3G, the sourceserving GPRS support node (SGSN) finds a source base station (i.e., asource RNC) according to the identifier of the RNC to which the sourcecell belongs or the extended identifier of the RNC. If the source accesssystem is LTE, the source mobility management entity (MME) finds asource eNB according to the cell identifier of the source cell.

In embodiments of the present disclosure, in a method for supportingindication of a failure event to a source access system, the sourceaccess notifies information of the source cell to the target accesssystem. When needing to transmit the message to the source accesssystem, the target access system routes the needed message to the basestation or a base station controller of the source access system throughthe core network by use of the information of the source cell receivedfrom the source access system. The target access system notifies aproblem of MRO between different RATs to the source access system, so asto avoid impact for a UE, reduce operator configuration. Thus, theproblem of the MRO between different RATs is addressed, and theperformance of the mobile communication system is improved.

Other aspects, advantages, and salient features of the disclosure willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses various embodiments of the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram illustrating a structure of a systemarchitecture evolution (SAE) system according to the related art;

FIG. 2 is a schematic diagram illustrating a basic principle ofself-optimizing an SAE system according to the related art;

FIG. 3 is a flowchart illustrating a method for supporting indication ofa failure event to a source access system according to an embodiment ofthe present disclosure;

FIG. 4 is a schematic diagram illustrating a method for supportingindication of a failure event to a source access system according to afirst embodiment of the present disclosure;

FIG. 5 is a schematic diagram illustrating a method for indicating afailure event to a source access system according to a first embodimentof the present disclosure;

FIG. 6 is a schematic diagram illustrating a method for supportingindication of a failure event to a source access system according to asecond embodiment of the present disclosure;

FIG. 7 is a schematic diagram illustrating a method for indicating afailure event to a source access system according to a second embodimentof the present disclosure.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of variousembodiments of the present disclosure as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the various embodiments describedherein can be made without departing from the scope and spirit of thepresent disclosure. In addition, descriptions of well-known functionsand constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of the presentdisclosure. Accordingly, it should be apparent to those skilled in theart that the following description of various embodiments of the presentdisclosure is provided for illustration purpose only and not for thepurpose of limiting the present disclosure as defined by the appendedclaims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide.

In order to address issues of the related art, the present disclosureprovides a method for supporting indication of a failure event to asource access system, i.e., notifying, by the source access system,information of a source cell to a target access system, transmitting, bythe target access system, a message to the source access system when thetarget access system needs to transmit the message to the base stationto which the source cell belongs.

By applying the method provided by the present disclosure, a problem ofmobility robustness optimization (MRO) among different radio accesstechnology (RAT) may be notified to source access systems, impact for aterminal is avoided, operator configuration is reduced. Thus, the issueof the MRO among different RATs are addressed, system performance isimproved.

In order to clarify the technical scheme and advantages of the presentdisclosure, the present disclosure is described further hereinafter withreference to accompanying drawings and examples.

FIG. 3 is a flowchart illustrating a method for supporting indication ofa failure event to a source access system an embodiment of the presentdisclosure.

Referring to FIG. 3, the operation includes the process provided below.

In operation 301, the source access system notifies information of asource cell to a target access system. The information of the sourcecell includes one or more of the following information: a cellidentifier of the source cell, a location area identity (LAI) to whichthe source cell belongs, a routing area code (RAC) to which the sourcecell belongs, an identifier of the radio network controller (RNC) towhich the source cell belongs, an extended identifier of the RNC towhich the source cell belongs, and a tracking area identity (TAI) towhich the source cell belongs.

The source access system notifies the information above of a basestation to which the source cell belongs to a target cell through arelocation required message, a handover required message, a forwardingrelocation request message, a relocation request message or a handoverrequest message. Alternatively, the source access system may transmitthe information to the base station to which the target cell belongsthrough a transparent container in the messages from a source to atarget.

In operation 302, when needing to transmit a message to the base stationto which the source cell belongs, the target access system transmits themessage to the source access system. The target access system knows thesource base station information according to the received information ofthe source cell. The information of the source cell is used for routingthe message from the target base station to the source base station.

Specifically, when the target access system detects that the source celltriggers unsuitable inter-RAT handover to the target cell, the targetaccess system transmits a message to the base station to which thesource cell belongs, notifies the unsuitable inter-RAT handover to thebase station to which the source cell belongs, e.g., too early inter-RAThandover or handover to an wrong RAT. The message includes the cellidentifier of the source cell, and/or the LAI to which the source cellbelongs, and/or the RAC to which the source cell belongs, and/or theidentifier of the RNC to which the source cell belongs, and/or theextended identifier of the RNC to which the source cell belongs, and/orthe TAI to which the source cell belongs.

According to the LAI and RAC or TAI to which the source cell belongs, anode of a target core network (e.g., a mobility management entity (MME)or a serving GPRS support node (SGSN) or a mobile switching center(MSC)) finds a node of a source core network (e.g., an MME or a SGSN oran MSC). If the source access system is 3G, the node of the target corenetwork finds a source SGSN according to the LAI and/or the RAC. If thesource access system is LTE, the node of the target core network finds asource MME according to the TAI. If the source access system is 3G, thesource SGSN finds a source base station (i.e., a source RNC) accordingto the identifier of the RNC to which the source cell belongs or theextended identifier of the RNC. If the source access system is LTE, thesource MME finds a source evolved Node B (eNB) according to the cellidentifier of the source cell.

Thereafter, the whole operation of the method for supporting indicationof a failure event to a source access system provided by the presentdisclosure ends.

FIG. 4 is a schematic diagram illustrating a method for supportingindication of a failure event to a source access system according to afirst embodiment of the present disclosure.

Referring to FIG. 4, the operation includes the process provided below.

In operation 401, an RNC determines handover. The RNC transmits arelocation required message to an SGSN. The message includes informationof a source cell. The information of the source cell includes one ormore kinds of the following information: a cell identifier of the sourcecell, a LAI to which the source cell belongs, a RAC to which the sourcecell belongs, an identifier of the RNC to which the source cell belongs,and an extended identifier of the RNC to which the source cell belongs.

In operation 402, the SGSN transmits a forwarding relocation requestmessage to an MME. The message includes information of the source cell.The information of the source cell is same as that in operation 401,which is not described repeatedly herein.

In operation 403, the MME transmits a handover request message to aneNB. The message includes the information of the source cell. Theinformation of the source cell is same as that in operation 401, whichis not described repeatedly herein. The eNB saves the information of thesource cell.

In operation 404, the eNB transmits a handover request confirmationmessage to the MME.

In operation 405, the MME transmits a forwarding relocation responsemessage to the SGSN.

In operation 406, the SGSN transmits a relocation command message to theRNC.

In operation 407, the RNC transmit a handover command message from aUTRAN to the UE.

In operation 408, a UE transmit a completion of handover to anE-universal terrestrial radio access network (UTRAN) to the RNC.

Thereafter, the whole operation of the method for supporting indicationof a failure event to a source access system in accordance with a firstembodiment of the present disclosure ends.

FIG. 5 is a flowchart illustrating a method for indicating a failureevent to a source access system according to a first embodiment of thepresent disclosure.

For example, the embodiment may be used in the following scenario: anRNC just hand over a UE to eNB1 successfully in the first embodiment. Aradio link failure (RLF) occurs for the UE in the cell of the eNB1. Whenthe UE re-accesses to a LTE cell, e.g., accessing cell2 (i.e., a cellcontrolled by eNB2) or is handed over the cell2, the UE transmits asaved RLF report to a base station to which the cell2 belongs. Herein,after RLF in cell1, the UE may access a 3G cell, e.g., cell3 first, andthen returns to the cell2 of LTE or is handed to the cell2 of LTE.

Referring to FIG. 5, the operation includes the process provided below.

In operation 501, the RLF occurs in the cell of the eNB1 for the UE.

In operation 502, when the UE returns to a LTE cell, e.g., the UEestablishes an RRC connection or executes an RRC connectionre-establishment in the cell2 controlled by the eNB2 or is handed overto the cell2 of LTE, the UE indicates to the base station that the UEhas information of the RLF report in an RRC connection setup request oran RRC connection setup completion or an RRC connection re-establishmentrequest or an RRC connection re-establishment completion or a handovercompletion or an RRC connection re-configuration completion or other RRCmessages transmitted by the UE.

In operation 503, the eNB2 requests the UE to report the information ofthe RLF report. The UE transmits the saved RLF report to the eNB2. TheRLF report of the UE includes a cell identifier of a cell serving the UElastly before a failure occurs. Content of the RLF report of the UE isnot emphasis in the present disclosure, which is not described herein.

In operation 504, the eNB2 transmits a RLF indication message to a basestation serving the UE lastly before the failure occurs. The RLF reportof the UE includes the cell identifier of the cell serving the UE lastlybefore the failure occurs. The eNB2 transmits the RLF indication to thebase station of the cell where the failure occurs according to the cellidentifier. The RLF indication message includes the information the RLFreport received from the UE.

In operation 505, the eNB1 determines a failure reason. A determinationmethod is not the emphasis of the present disclosure, which is notdescribed herein.

In operation 506, the eNB1 transmits the failure reason to the basestation triggering the handover, e.g., too early inter-RAT handover,handover to a wrong RAT. The eNB1 transmits a handover report to an MME.The eNB1 may transmits the handover report to the MME through an eNBdirect transfer message or other S1 messages. The message includes a LAIto which the cell triggering the handover belongs and an identifier ofthe RNC to which the cell triggering the handover belongs, may furtherinclude a RAC to which the cell triggering the handover belongs or anextended identifier of the RNC to which the cell triggering the handoverbelongs. The message may further include a cell identifier of the sourcecell triggering the handover, and/or a cell identifier of the targetcell of the last handover before failure, and/or the failure reasone.g., too early inter-RAT handover or handover to an wrong RAT or acell. During a handover operation, information, such as the LAI of thesource cell, the identifier of the RNC, and/or the RAC, and/or theextended identifier of the RNC, and the like, has already been saved.

In operation 507, the MME transmits a handover report to the SGSN. TheMME finds the SGSN according to the LAI and/or the RAC in the receivedmessage.

In operation 508, the SGSN transmits the received handover report to theRNC. The SGSN finds the RNC according to the identifier of the RNC orthe extended identifier of the RNC. The RNC counts problems of MROaccording to the failure reason and the cell identifier of the sourcecell and the target cell of the handover at the last time before thefailure occurs.

Thereafter, the whole operation of the method for indicating a failureevent to a source access system in accordance with an embodiment of thepresent disclosure ends.

FIG. 6 is a schematic diagram illustrating a method for supportingindication of a failure event to a source access system according to asecond embodiment of the present disclosure.

Referring to FIG. 6, the operation includes the process provided below.

In operation 601, an eNB determines handover. The eNB transmits ahandover required message to an MME. The message includes information ofa source cell. The information of the source cell includes one or moreof the following information: an identifier of the source cell, and aTAI to which the source cell belongs.

In operation 602, the MME transmits a forwarding relocation requestmessage to an SGSN. The message includes the information of the sourcecell. The information of the source is same as in operation 601, whichis not described repeatedly herein.

In operation 603, the SGSN transmits a relocation request message to anRNC. The message includes the information of the source cell. Theinformation of the source is same as in operation 601, which is notdescribed repeatedly herein.

In operation 604, the RNC transmits a relocation request confirmationmessage to the SGSN.

In operation 605, the SGSN transmits a forwarding relocation responsemessage to the MME.

In operation 606, the MME transmits a handover command message to theeNB.

In operation 607, the eNB transmits a handover command message to theUE.

In operation 608, the UE transmits a handover completion from a UTRAN tothe RNC.

Thereafter, the whole operation of the method for supporting indicationof a failure event to a source access system in accordance with a secondembodiment of the present disclosure ends.

FIG. 7 is a flowchart illustrating a method for indicating a failureevent to a source access system according to a second embodiment of thepresent disclosure.

For example, the embodiment may be used in the follow scenario: in anembodiment in FIG. 6, an eNB just hands over a UE to RNC1 successfully.A RLF occurs for the UE in a cell of the RNC1. When the UE re-accesses a3G cell, e.g., accessing cell 2 (a cell controlled by RNC2) or is handedover to the cell 2, the UE transmits information of a saved RLF reportto the RNC of the cell 2. Herein, after a failure occurs when the UEaccesses the cell 1, the UE may access a LTE cell, such as cell 3 first,and then returns to the cell 2 of 3G or is handed over to the cell 2 of3G.

Referring to FIG. 7, the operation includes the process provided below.

In operation 701, the RLF occurs in the cell of the RNC1 for the UE.

In operation 702, when the UE returns to a cell of 3G, e.g., the UE setsup an RRC connection in the cell 2 controlled by the RNC2 or is handedover to the cell 2 of 3G, the UE indicates to the RNC2 that the UE hasinformation of the RLF report in an RRC connection setup request or anRRC connection setup completion or an RRC connection re-establishmentrequest or an RRC connection re-establishment completion or a handovercompletion or an RRC connection re-configuration completion or other RRCmessages transmitted by the UE.

In operation 703, the RNC2 requests the UE to report the information ofthe RLF report. The UE transmits the saved RLF report to the RNC2. TheRLF report of the UE includes a cell identifier of a cell serving the UElastly before the failure occurs. Content of the RLF report of the UE isnot emphasis of the present disclosure, which is not described herein.

In operation 704, the RNC2 transmits a RLF indication message to theRNC1 serving the UE lastly before the failure occurs. The message may betransmitted to the RNC1 through an Iur interface or an Iu interfacethrough a core network. The RLF report of the UE includes the cellidentifier of the cell serving the UE lastly before the failure occurs.The RNC2 transmits the RLF indication message to the RNC to which thecell where the RLF occurs belongs according to the cell identifier. TheRLF indication message includes the information of the RLF report of theUE received from the UE.

In operation 705, the RNC1 determines a failure reason. A determinationmethod is not the emphasis of the present disclosure, which is notdescribed herein.

In operation 706, the RNC1 transmits the failure reason to the basestation triggering the handover, e.g., too early inter-RAT handover,handover to a wrong RAT. The RNC1 transmits a handover report to a SGSN.The RNC1 may transmit the handover report to the SGSN through a way of aRAN information management (RIM) or other Iu messages. The messageincludes a TAI to which the cell triggering the handover belongs. Themessage also includes a cell identifier of the source cell triggeringthe handover, and/or a cell identifier of the target cell of the lasthandover, and/or the failure reason e.g., too early inter-RAT handoveror handover to an wrong RAT or cell. The identifier of the TAI of thesource cell and the cell identifier of the source cell have already beensaved during a handover operation.

In operation 707, the SGSN transmits the handover report to the MME. TheSGSN finds the MME according to the TAI in the received message.

In operation 708, the MME transmits the received handover report to theeNB. The MME finds the eNB according to the cell identifier of thesource cell in the received message. The eNB counts problems of MROaccording to the failure reason and the identifier of the source celland the target cell of the handover at the last time before the failureoccurs in the received handover report.

Thereafter, the whole operation of the method for indication of afailure event to a source access system in accordance with a secondembodiment of the present disclosure ends.

In embodiments of the present disclosure, in a method for supportingindication of a failure event to a source access system, the sourceaccess transmits information of a source cell to a target base stationthrough handover. When a handover problem is detected by a cell of atarget base station, the target base station may transmit an event of ahandover failure to a base station of the source cell according to theinformation of the source cell. Thus, correct self-optimization may beperformed for a mobile communication system according to a detectedreason, to improve performance of the mobile communication system.

While the present disclosure has been shown and described with referenceto various embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present disclosure asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for executing a handover in acommunication system, the method comprising: receiving, by a first basestation (BS) of a first radio access technology (RAT) which is differentfrom a second RAT, from a second BS of the second RAT, cell informationincluding a cell identifier related to a cell of the second BS;detecting, by the first BS, an unnecessary inter-RAT handover from thesecond RAT to the first RAT; and transmitting, by the first BS, to thesecond BS, a handover report including the cell identifier in responseto detection of the unnecessary inter-RAT handover, wherein the cellinformation is used to identify the cell of the second BS in theunnecessary inter-RAT handover.
 2. The method of claim 1, wherein thecell identifier is an E-UTRAN cell global identifier (ECGI) of the cell.3. The method of claim 1, wherein the cell information further includesa tracking area identity (TAI).
 4. The method of claim 1, wherein thecell information is received in a handover preparation procedure.
 5. Themethod of claim 1, wherein the cell information is included in atransparent container transmitted from the second BS to the first BS. 6.A first base station (BS) of a first radio access technology (RAT) in acommunication system, the first BS comprising: a transceiver; and atleast one processor configured to: control the transceiver to receive,from a second BS of a second RAT which is different from the first RAT,cell information including a cell identifier related to a cell of thesecond BS, detect an unnecessary inter-RAT handover from the second RATto the first RAT, and control the transceiver to transmit, to the secondBS, a handover report including the cell identifier in response todetection of the unnecessary inter-RAT handover, wherein the cellinformation is used to identify the cell of the second BS in theunnecessary inter-RAT handover.
 7. The first BS of claim 6, wherein thecell identifier is an E-UTRAN cell global identifier (ECGI) of the cell.8. The first BS of claim 6, wherein the cell information furtherincludes a tracking area identity (TAI).
 9. The first BS of claim 6,wherein the cell information is included in a transparent containertransmitted from the second BS to the first BS.
 10. The first BS ofclaim 6, wherein the cell information is received in a handoverpreparation procedure.
 11. A method for executing a handover in acommunication system, the method comprising: transmitting, by a secondbase station (BS) of a second radio access technology (RAT), to a firstBS of a first RAT which is different from the second RAT, cellinformation including a cell identifier related to a cell of the secondBS; triggering, by the second BS, an inter-RAT handover from the secondRAT to the first RAT; and receiving, by the second BS, from the firstBS, a handover report including the cell identifier in response todetecting, by the first BS, the inter-RAT handover as an unnecessaryinter-RAT handover, wherein the cell information is used to identify thecell of the second BS in the unnecessary inter-RAT handover.
 12. Themethod of claim 11, wherein the cell identifier is an E-UTRAN cellglobal identifier (ECGI) of the cell.
 13. The method of claim 11,wherein the cell information further includes a tracking area identity(TAD.
 14. The method of claim 11, wherein the cell information istransmitted in a handover preparation procedure.
 15. The method of claim11, wherein the cell information is included in a transparent containertransmitted from the second BS to the first BS.
 16. A second basestation (BS) of a second radio access technology (RAT) in acommunication system, the second BS comprising: a transceiver; and atleast one processor configured to: control the transceiver to transmit,to a first BS of a first RAT which is different from the second RAT,cell information including a cell identifier related to a cell of thesecond BS, trigger an inter-RAT handover from the second RAT to thefirst RAT, and control the transceiver to receive a handover reportincluding the cell identifier in response to detecting, by the first BS,the inter-RAT handover as an unnecessary inter-RAT handover, wherein thecell information is used to identify the cell of the second BS in theunnecessary inter-RAT handover.
 17. The second BS of claim 16, whereinthe cell identifier is an E-UTRAN cell global identifier (ECGI) of thecell.
 18. The second BS of claim 16, wherein the cell informationfurther includes a tracking area identity (TAI).
 19. The second BS ofclaim 16, wherein the cell information is included in a transparentcontainer transmitted from the second BS to the first BS.
 20. The secondBS of claim 16, wherein the cell information is transmitted in ahandover preparation procedure.